I got mine from Winchline (Viking off road), mostly because they gave me a free hat . Its Amsteel blue line - and shipping was quick.

One thing to consider with the length. If most of your pulls are way under 125', then you could get a shorter rope (say 80') to maximize the strength of the winch. And then carry an extra 50' extension if you think you might need it for really long pulls. Advantages: less weight on the front end of the truck, more pulling strength on the "average" pull, and the ability (if needed) to go with a bigger diameter rope spooled on your winch.

One other thing - are you going to upgrade your fairlead? Steel rollers, especially those already used with steel line, can damage the synth rope. Better to get a hawse fairlead, or some delrin rollers to pair with your new line.

I get mine from Rockstomper, I put on the same length of cable that came off, and I generally replace it every few years to be safe, but no breaks yet. I have had some fairly hard pulls and all is good. I will never use cable again, much harder to use than rope

I don't like how synthetic coils up when it's laying on the ground (just like a rope), it's easy for it to get tied into knots, grab sticks, etc. I also don't like how it feels like parts of it are being shaved off by my glove, as I provide some resistance to it when recoiling. I'm sticking with the steel cable until I see the need to replace it, then we'll see.. for now I can think of much better places to spend $300.